Liquefied carbon dioxide is a very cold cryogenic fluid and is stored in Dewar-type containers under high pressure. When liquefied carbon dioxide is brought into contact with a low surrounding pressure, such as less than 70 psig, the liquid assumes a crystalline form called carbon dioxide snow. With time and the absorption of heat, the carbon dioxide snow sublimates and returns to its normal gaseous state. Because the carbon dioxide snow absorbs large quantities of heat during the sublimation process, it is used in place of ice for cooling substances and/or for keeping a substance in a frozen state. The rate of sublimation for carbon dioxide snow is dependent upon the ambient temperature and pressure surrounding said snow and upon the surface area of the snow which is available for heat absorption. From a theoretical point of view, as the carbon dioxide snow particles become larger and larger the surface area for a given total mass of snow becomes smaller and smaller. Therefore, it becomes desirable to maximize the density of the snow produced in order to minimize the rate of sublimation. Because of this, it has become common practice to collect carbon dioxide snow and to compress that snow into larger blocks of solid material. With the application of sufficient pressure during the compression process a block of nearly 100 per cent solid carbon dioxide can be formed. The purpose of this compression process is to minimize the surface area of the solid carbon dioxide that is available for sublimation while maximizing the density and quantity of compressed solid carbon present thus greatly extending the time required to convert the solid carbon dioxide to its gaseous state.